[PATCH] libata: implement ata_drive_probe_reset()

Most low level drivers share supported reset/classify actions and
sequence.  This patch implements ata_drive_probe_reset() which helps
constructing ->probe_reset from three component operations -
softreset, hardreset and postreset.  This minimizes duplicate code and
yet allows flexibility if needed. The three component operations can
also be shared by EH later.

Signed-off-by: Tejun Heo <htejun@gmail.com>
Signed-off-by: Jeff Garzik <jgarzik@pobox.com>